1. Technical Field
The present invention relates to an electronic component module, and particularly to an electromagnetic wave shielding structure of an electronic component module.
2. Description of Related Art
With the aim of preventing the leak of electromagnetic wave noise from an electronic component such as a semiconductor chip and preventing the intrusion of electromagnetic wave noise from a surrounding environment, the periphery of the electronic component has been covered with an electromagnetic wave shield made of metal film. In recent years, the electronic components have been required to be smaller in size and have a higher performance. As a result, the electromagnetic wave shields, too, are required to be made smaller in size and have a high performance.
For example, an electronic component shielding method disclosed in Japanese Patent Application Laid-Open No. 2012-151326 includes: a step of sealing a semiconductor device mounted on a substrate with a sealing resin containing a filler; a step of shaving a surface of the sealing resin to expose a part of the filler; a step of carrying out etching of the exposed filler to make a hole on the surface of the sealing resin; and a step of forming a metal film on the surface of the sealing resin including an inner surface of the hole. This shielding method improves the anchor effect of the metal film, leading to an improvement in the adhesion of the metal film to the surface of the sealing resin. Moreover, the metal film that serves as the electromagnetic shielding layer is directly formed on the surface of the sealing resin. Therefore, the entire semiconductor device, including the electromagnetic shield, can be made smaller in size than when the entire component is covered with a metal plate.
Japanese Patent Application Laid-Open No. 2013-080926 discloses a substrate module that includes an EMI (Electro Magnetic Interference) shielding layer. The substrate module includes a semiconductor package and an EMI shielding layer formed at least in one portion of the surface of the semiconductor package. The EMI shielding layer contains a matrix layer, a metal layer disposed in an upper portion of the matrix layer, and first seed particles disposed at an interface between the matrix layer and the metal layer. The substrate module can be extended in such a way as to allow a conventional shielding step, which has been conducted on a per-device basis, to be carried out at the level of the mounting substrate. Therefore, the module can be produced inexpensively and with high productivity in a short period of time.
However, the problem with the above-described conventional electromagnetic wave shielding structure is that the adhesion of the metal film to the electronic component is weak, and the durability (humidity resistance) thereof is low.
For example, as shown in FIGS. 4 and 5 of Japanese Patent Application Laid-Open No. 2012-151326, if a difference in level is generated on the surface of the sealing resin and on an inner surface of a hole formed on the surface of the sealing resin, the amount of plating solution that goes around to a surface of the inner surface of the hole may be insufficient during an electroless plating process, and the plating may not adhere thereto. Therefore, the problem is that a sufficient electromagnetic shielding performance cannot be obtained, and the durability is low. Moreover, since the unevenness of the inner surface of the hole is large, a water washing process that comes after the electroless plating process could be often insufficient; the plating solution remaining on the inner surface of the hole could lead to a decrease in reliability.